lookupDynamic

1-D interpolated lookup with breakpoints and table taken from input ports.

📝Syntax

Block type: lookupDynamic

📥Input Arguments

Parameter	Description
input ports	3 input port(s) declared.

📤Output Arguments

Parameter	Description
output ports	1 output port(s) declared.

📄Description

1-D interpolated lookup with breakpoints and table taken from input ports.

Module	`nflow_blocks`
Library	Lookup Tables
Type	`lookupDynamic`
Label	Lookup Table Dynamic

Description

A 1-D linearly interpolated lookup whose breakpoint and table data come from input ports instead of parameters, so the table can change at run time. Port 0 = value x; port 1 = breakpoint vector xdat (strictly increasing); port 2 = table vector ydat (same length). The output is the linear interpolation of (xdat, ydat) at x, clipped outside the range.

Native runtime (the run-time vector table is a follow-up for code generation).

Ports

Input(s)

Port	Role	Side	Position
Port_1	Numeric signal read by the block.	left	x=0, y=20
Port_2	Numeric signal read by the block.	left	x=0, y=40
Port_3	Numeric signal read by the block.	left	x=0, y=60

Output(s)

Port	Role	Side	Position
Port_1	Numeric signal produced by the block.	right	x=90, y=40

Parameters

Parameter	Default value
none

Block Characteristics

Block type	lookupDynamic
Family	Lookup Tables
Rendered size	90 x 80
Phases	ALGEBRAIC
Internal state or history	no
Signal data type	double numeric values

Algorithms

ALGEBRAIC: locate the interval in xdat, interpolate ydat linearly, clip outside range.

Equation or Rule

$$y = \text{interp}(\text{xdat}, \text{ydat}, x)$$

Extended Capabilities

Code generation: supported for C and Rust.

Implementation Sources

Manifestmodules/nflow_blocks/libraries/lookup/library.json

{
  "id": "builtin.lookup",
  "title": "Lookup Tables",
  "version": "0.1.0",
  "format": "nflow-2",
  "builtin": true,
  "blocks": [
    {
      "type": "lookup1D",
      "label": "1-D Lookup Table",
      "icon": "lookup1D.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 90,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 90,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {
        "BreakpointsForDimension1": [
          0,
          1,
          2,
          3,
          4
        ],
        "Table": [
          0,
          1,
          4,
          9,
          16
        ],
        "InterpMethod": "Linear point-slope",
        "ExtrapMethod": "Linear"
      },
      "render": {
        "type": "image",
        "src": "exports/lookup1D.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 90,
        "height": 80
      }
    },
    {
      "type": "lookup2D",
      "label": "2-D Lookup Table",
      "icon": "lookup2D.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 90,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 30,
          "side": "left"
        },
        {
          "x": 0,
          "y": 50,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 90,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {
        "BreakpointsForDimension1": [
          1,
          2,
          3
        ],
        "BreakpointsForDimension2": [
          1,
          2,
          3
        ],
        "Table": [
          4,
          5,
          6,
          5,
          7,
          8,
          6,
          8,
          10
        ],
        "InterpMethod": "Linear point-slope",
        "ExtrapMethod": "Linear"
      },
      "render": {
        "type": "image",
        "src": "exports/lookup2D.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 90,
        "height": 80
      }
    },
    {
      "type": "lookupND",
      "label": "n-D Lookup Table",
      "icon": "lookupND.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 90,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 30,
          "side": "left"
        },
        {
          "x": 0,
          "y": 50,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 90,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {
        "NumberOfTableDimensions": 2,
        "BreakpointsForDimension1": [
          1,
          2,
          3
        ],
        "BreakpointsForDimension2": [
          1,
          2,
          3
        ],
        "Table": [
          4,
          5,
          6,
          5,
          7,
          8,
          6,
          8,
          10
        ],
        "InterpMethod": "Linear point-slope",
        "ExtrapMethod": "Linear"
      },
      "render": {
        "type": "image",
        "src": "exports/lookupND.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 90,
        "height": 80
      }
    },
    {
      "type": "directLookup",
      "label": "Direct Lookup Table (n-D)",
      "icon": "directLookup.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 90,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 30,
          "side": "left"
        },
        {
          "x": 0,
          "y": 50,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 90,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {
        "NumberOfTableDimensions": 2,
        "TableDimensions": [
          2,
          3
        ],
        "Table": [
          0,
          1,
          10,
          11,
          20,
          21
        ]
      },
      "render": {
        "type": "image",
        "src": "exports/directLookup.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 90,
        "height": 80
      }
    },
    {
      "type": "prelookup",
      "label": "Prelookup",
      "icon": "prelookup.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 90,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 90,
          "y": 30,
          "side": "right"
        },
        {
          "x": 90,
          "y": 50,
          "side": "right"
        }
      ],
      "defaultParams": {
        "BreakpointsForDimension1": [
          0,
          1,
          2,
          3,
          4
        ]
      },
      "render": {
        "type": "image",
        "src": "exports/prelookup.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 90,
        "height": 80
      }
    },
    {
      "type": "interpolationPrelookup",
      "label": "Interpolation Using Prelookup",
      "icon": "interpolationPrelookup.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 90,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 30,
          "side": "left"
        },
        {
          "x": 0,
          "y": 50,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 90,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {
        "Table": [
          0,
          1,
          4,
          9,
          16
        ]
      },
      "render": {
        "type": "image",
        "src": "exports/interpolationPrelookup.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 90,
        "height": 80
      }
    },
    {
      "type": "lookupDynamic",
      "label": "Lookup Table Dynamic",
      "icon": "lookupDynamic.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 90,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 20,
          "side": "left"
        },
        {
          "x": 0,
          "y": 40,
          "side": "left"
        },
        {
          "x": 0,
          "y": 60,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 90,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {},
      "render": {
        "type": "image",
        "src": "exports/lookupDynamic.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 90,
        "height": 80
      }
    }
  ]
}

Runtimemodules/nflow_blocks/src/cpp/lookup/lookupDynamic.cpp

//=============================================================================
// Copyright (c) 2016-present Allan CORNET (Nelson)
//=============================================================================
// This file is part of Nelson.
//=============================================================================
// LICENCE_BLOCK_BEGIN
// SPDX-License-Identifier: LGPL-3.0-or-later
// LICENCE_BLOCK_END
//=============================================================================
// lookupDynamic (Lookup Table Dynamic): a 1-D linearly interpolated lookup whose
// breakpoint and table data come from input ports instead of parameters, so the
// table can change at run time. Port 0 = value x; port 1 = breakpoint vector
// xdat (strictly increasing); port 2 = table vector ydat (same length). Output =
// linear interpolation of (xdat, ydat) at x, clipped outside the range.
// Feedthrough (ALGEBRAIC), real double, scalar output. Native runtime only: no
// code generation for the run-time vector table.
//=============================================================================
#include "SimEngineTypes.hpp"
#include "BlockRegistry.hpp"
#include "FieldNames.hpp"
#include "NFlowBlockDescriptor.hpp"
#include "lookup_blocks.hpp"
#include <vector>
//=============================================================================
namespace Nelson {
//=============================================================================
namespace NFlow {
    //=============================================================================
    // Read the table (port 2) with breakpoint indices (0..n-1, n = breakpoint
    // width). The index is clamped so a saved model that wires a table port
    // narrower than the breakpoint vector cannot read past the table region.
    // A width-1 table still broadcasts through sigAt().
    static inline double
    lookupTableAt(const SigView& yd, int i)
    {
        if (yd.width > 1 && i >= yd.width) {
            i = yd.width - 1;
        }
        return sigAt(yd, i);
    }
    //=============================================================================
    bool
    handleLookupDynamic(SimCtx& ctx, const Block& b, Phase phase)
    {
        if (phase != Phase::ALGEBRAIC) {
            return false;
        }
        if (!hasInput(ctx, b.nid, 0) || !hasInput(ctx, b.nid, 1) || !hasInput(ctx, b.nid, 2)) {
            return false;
        }
        const double x = getInput(ctx, b.nid, 0, 0.0);
        SigView xd = getInputSig(ctx, b.nid, 1);
        SigView yd = getInputSig(ctx, b.nid, 2);
        const int n = xd.width;
        double out = 0.0;
        if (n <= 0) {
            out = 0.0;
        } else if (n == 1) {
            out = lookupTableAt(yd, 0);
        } else if (x <= sigAt(xd, 0)) {
            out = lookupTableAt(yd, 0);
        } else if (x >= sigAt(xd, n - 1)) {
            out = lookupTableAt(yd, n - 1);
        } else {
            int i = n - 2;
            while (i > 0 && x < sigAt(xd, i)) {
                --i;
            }
            const double x0 = sigAt(xd, i);
            const double x1 = sigAt(xd, i + 1);
            const double d = x1 - x0;
            const double f = (d != 0.0) ? (x - x0) / d : 0.0;
            const double y0 = lookupTableAt(yd, i);
            const double y1 = lookupTableAt(yd, i + 1);
            out = y0 + f * (y1 - y0);
        }
        setOutput(ctx, b.nid, out);
        return false;
    }
    //=============================================================================
    bool
    resolveLookupDynamicDims(const Block& b, const ValMap& vars, const std::vector<PortSig>&,
        std::vector<PortSig>& outSigs, std::string&)
    {
        (void)b;
        (void)vars;
        outSigs[0].setVector(1);
        outSigs[0].type = SigType::Double;
        return true;
    }
    //=============================================================================
} // namespace NFlow
//=============================================================================
} // namespace Nelson
//=============================================================================

💡Examples

Interpolate ydat=[0 1 4 9 16] over xdat=[0 1 2 3 4] at x=2.5 -> 6.5.

d.blocks={ struct('id','x','type','constant','inputs',0,'outputs',1,'params',struct('Value',2.5)), struct('id','xd','type','constant','inputs',0,'outputs',1,'params',struct('Value',[0 1 2 3 4])), struct('id','yd','type','constant','inputs',0,'outputs',1,'params',struct('Value',[0 1 4 9 16])), struct('id','ld','type','lookupDynamic','inputs',3,'outputs',1,'params',struct()), struct('id','w','type','toWorkspace','inputs',1,'outputs',0,'params',struct('VariableName','y','SaveFormat','Array')) };
d.connections={ struct('from','x','to','ld','fromIndex',0,'toIndex',0), struct('from','xd','to','ld','fromIndex',0,'toIndex',1), struct('from','yd','to','ld','fromIndex',0,'toIndex',2), struct('from','ld','to','w','fromIndex',0,'toIndex',0) };
d.sampleTime=0.1; d.duration=0.2; d.solver='discrete'; d.variables=struct();
r=jsondecode(__nflow_simulate__(jsonencode(d)));

🔗See Also

lookup1D prelookup

🕔Version History

Version	Description
1.0.0	initial version

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